344 PRACTICAL ORGANIC CHEMISTRY ti 1 distillation (if a liquid) or by crystallisation (if a solid), shake with caustic soda solution. This will dissolve the acid or phenol, and the insoluble constituent may be removed mechanically or, if volatile, by distillation in steam, by extraction with ether or, if solid, by filtration. Acid and Phenol, if present together, may be separated by adding sodium bicarbonate in excess and extracting with ether, or by dissolving in caustic soda solution, saturating with carbon dioxide and then extracting with ether. The ether extracts the phenol, which is insoluble in sodium carbonate, leaving the acid. Ester and Hydrocarbon may be separated by hydrolysis, which decomposes the ester, but not the hydrocarbon. Paraffin and Aromatic Hydrocarbon may be separated by the action of fuming sulphuric acid, which forms the sulphonic acid with the aromatic hydrocarbon. The product is poured into water. The sulphonic acid dissolves readily in water, whereas the paraffin is insoluble. A mine or Base may be separated from the majority of insoluble organic substances by shaking it with dilute hydro- chloric acid, with which it forms the soluble hydrochloride. Aldehyde or Ketone may be separated from the other constituents by shaking the liquid, which should be free from water, with a saturated solution of sodium bisulphite, and de- canting or filtering the liquid residue. If the liquid is soluble in water, like ethyl alcohol, it may precipitate the bisulphite of sodium. This is prevented by adding a little ether before introducing the bisulphite into the liquid. In separating two liquids in a test-tube, for example, an ethereal from an aqueous solution, either the ether may be decanted or it may be desirable to withdraw the lower aqueous layer. This is done by sucking the liquid into a small .pipette furnished with a mouth-piece of rubber tubing, which may be nipped when the requisite quantity is removed. The pipette is then withdrawn, keeping the rubber tube tightly closed, and the liquid transferred to another test-tube. It is often advisable to adopt this method previous to decanting the top layer, which is much more effectively separated from a small than from a .large quantity of the aqueous layer.